1. Field of the Invention
The invention is related to the field of memories and, in particular, to a three-dimensional magnetic memory comprised of a stack of data storage layers. More particularly, the data storage layers of the three-dimensional magnetic memory are formed from multi-layer structures.
2. Statement of the Problem
Solid-state memory is a nonvolatile storage medium that uses no moving parts. Some examples of solid-state memory are flash memory and MRAM (magnetoresistive random access memory). Solid-state memories provide advantages over conventional disk drives in that data transfers to and from solid-state memories take place at a much higher speed than is possible with electromechanical disk drives. Solid-state memories may also have a longer operating life and may be more durable due to the lack of moving parts. One problem with traditional solid-state memories is that storage capacity is much less than can be achieved with electromechanical disk drives. For instance, a common flash memory may store up to approximately 1 gigabyte (GB), whereas a common hard drive may store up to 100 GB or more. The cost per megabyte is higher for solid-state memories than for electromechanical disk drives.
Solid-state memories have a size that is determined by a minimum feature size (F). One problem with solid-state magnetic memories (as opposed to flash memory) is the cell density of the memory. A typical solid-state magnetic memory has a cell size that is large compared to flash memories due to the nature of magnetic fields from current lines extending over a typical 4F distance range. For instance, an MRAM may have a cell size of 32 F2 while a flash memory may have a cell size of 4 F2. The larger cell size of solid-state magnetic memories unfortunately relates to a reduced cell density.
It may thus be desirable to design solid-state magnetic memories that have reduced cell size.